1. Field of the Invention
The present invention relates generally to avionics instrumentation and, more specifically, to outfitting and/or retrofitting aircraft with electronic instruments.
2. Description of the Related Art
Aircraft cockpit flight instrumentation (avionics) indicators may employ a variety of mechanisms, including vertical scale indicator mechanisms, radial dial indicator mechanisms, and pivoting mechanisms, such as those of compasses and attitude gyro indicators.
Many avionics indicators have long been entirely electro-mechanical, with needle pointers, rotating wheels, bands, spheres and so forth moving over or within a fixed dial or housing. For example, a needle pointer gauge that is used to indicate an operating pressure or temperature commonly has a circular housing, with a scale printed circumferentially along its perimeter, and a pointer needle that pivots about a central axis and alongside the scale to indicate the temperature or pressure. A pilot can, for example, determine at a glance that a measured temperature or pressure is abnormal when the pointer needle is pointing to a point above or below where it normally points during nominal conditions. A pilot can read the specific temperature or pressure by noting the point on the scale to which the pointer needle points.
Although fully solid-state display-based technologies, such as multi-function display instruments, have begun to supplant electro-mechanical indicators in newer commercial and military aircraft, in many existing aircraft the older, electro-mechanical indicators are still very common. For example, in general aviation (i.e., small private aircraft) pilots and regulatory authorities have been slower to accept changing over to solid-state display-based technologies. This is so in part because general aviation pilots generally are more accustomed to the appearance of mechanical instruments. For example, in older CESSNA CITATION aircraft, electro-mechanical vertical scale indicators are used to indicate fuel flow, inter-turbine temperature, fan speed and turbine speed. It would be desirable to retrofit such older aircraft with solid-state electronic display-based instruments, but retrofitting these aircraft with the latest multi-function display instruments generally is impractical and costly because their form factors differ greatly from those of the original instruments, and it can be difficult to obtain approval from regulatory authorities.
Accordingly, it can be seen that a need yet exists for a method and apparatus to replace existing electro-mechanical avionics display instruments, while allowing the replacement instrument to be fitted within the existing openings of the aircraft. It is to the provision of such a method and apparatus that the present invention is primarily directed.